Phenolic solutions of imide-amide polymers

ABSTRACT

The viscosity of solutions of amide-imide polymers in phenols having a melting point below 50*C is reduced by the addition to the solution of a saturated or ethylenically unsaturated carboxylic acid of up to 6 carbon atoms in an amount from 0.1 to 50% by weight; the reduction in viscosity facilitating the use of the solution, for example as coating compositions.

United States Patent [191 Ducloux et al.

[111 3,914,505 Oct. 21, 1975 [54] PHENOLIC SOLUTIONS OF IMIDE-AMIDEPOLYMERS [75] Inventors: Maurice Ducloux, Irigny; Max

Gruffax, La Mulatiere, both of France [73] Assignee: Rhone-Poulenc,S.A., Paris, France [22] Filed: Oct. 15, 1973 [21] Appl. No.: 406,461

[30] Foreign Application Priority Data Oct. 16, 1972 France 72.36574[52] US. Cl 428/379; 260/31.2 N; 260/33.4 P; 427/388; 428/458; 428/474[51] Int. C13... B051) 7/20; C08K 5/09; C08K 5/13; I C09D 3/70 [58]Field of Search 260/31.2 N, 33.4 P; 117/232,128.4, 161 P [56] ReferencesCited 9 UNITED STATES PATENTS 3,661,832 5/1972 Stephens 260/33.4 P

3,691,136 9/1972 Serres et al 260/33.4 P 3,692,740 9/1972 Suzuki eta1... 260/33.4 P 3,696,077 10/1972 Suzuki et a1... 260/33.4 P 3,803,l004/1974 lzumi et al..... 260/33.4 P 3,817,926 6/1974 Pauze et al.260/33.4 P

Primary Examiner-Allan Lieberman Attorney, Ageizt, or Firm--Stevens,Davis, Miller Mosher [57] ABSTRACT 9ECIaims, No Drawings PIIENOLICSOLUTIONS-F IMlDE-AMIDE' POLYMERS films by casting solutions with as'olids content greater than is of definite industrial value. Thepresent invention provides a process for lowering the viscosity of asolution of an imide-amide polymet in a phenolic solvent with a meltingpoint below 50C, or in a mixture of phenolic solvents, at least one ofwhich has a meltingfpoint below 50C, which comprises adding theretoa;.saturated or ethylenically unsaturated carboxylic .acidwith upto 6carbon atomsjnan amount which is g enerallyjrom 0.116 50% by weightbased on the weight-of the solution to:be ;rendered more fluid. J By.imide-amide.polymers as used herein, ;.t here;,are to, be, understood,polymers containing simultaneously imideand amide radicals.- Thesecambeproducedby condensation: r v a. of a diamine with an-amide groupanda'tetr'a'carboxylic acid dianhydride, I b. of a diamine with an imidegroup .and a tetracarboxylic acid dichloride,

c. of a diamine and a tricarboxylic acid chloride with an'anhydridegroup, 1 v d. of a diisocyanate and a tricarboxylic acid anhydride, l e.of a diurethane and a tricarboxylic acid anhydride, f. of a dianhydridewith an amide group and adiamine or a diisocyanate or a diurethane, org. of a diacidwithanimide group and a diisocyanate or a diurethane.

Imide-amide polymers-can also beproduced by combining processes (a) and(c), or (b) and (c), or (d)'and ),-0.r (d) n (g), 0 n (e (g) andNumerous documents describe the preparation of' such polymers, forexample New Linear. Polymers"-by H.=LEE, D. STOFFEY and C. NEVILLEMcGrawHill,-

p. 171 et seq. r

The. present invention relates particularly .topolytrimellitimide-amides. x

"The phenolic solvents .-withia melting point below ing point such as'pyrocatechol, resorcinoLvhydroquinone or phloroglucinol. 1

The saturated or ethylenically unsaturated carboxylic acidspreferab-lyemployed in the compositions according to the invention are formic-acid,acetic acid, propion'ic acid, butyric acid, acrylic acid, 'croton'icacid and methacrylic acid.

The amount of acid to be incorporated into the compositions in order toachieve'a given viscosity depends on the originalviscosity and on theinitial concentration of the imide-amide-solution. It is preferably from0.1 530% by weight relative to the solution to be rendered more fluid. I

The addition of acid, even at very low doses, makes it possible toproduce more fluid solutions, the final viscosity' ofwhi'ch changesonlyslig'htly on storage. The production of low viscosity solutions ofimide-amide polymers makes numerousapplications possible, for examplethe lacquering or impregnating of wires or coils of wiresfdr'the'electrical industry, and t'heco'ating ofnumerousothersubstrates, fdrexaniple metals in the form of'sheet metal,wiresorgaiize, glass in the form of shee't's'ffibres or woven fabric,and polymei'ic m'at erfl als in the form of sheets, fibres, foams, wovenor nonwoven fabrics'and coverings.

The use of very concentrated solutions of imideamide o sjwe wit asi sint a iattofpmdyc films by casting under good -conditio n s.

The following Examples further illustrate the present invention. .f i

400 g of ortho-cresol are introduced into a 1 liter glass reactor whichis equippedwith a stirrer and a thermometer and is placed in a waterbath thermostatically controlled at 50C: i of polytrinie'llitiniideamide, consisting essentiallyof re u ring units of t e formula:

having a reduced viscosity, measured at 25C at a con-i centration of 0.5g/cm in ortho-cresol, of 41.5 cmfg, containing 6.5% by weight ofN-methylpyrrolidone- (NMP) and 5.7% by weight of water, are introduced,in the form of a powder, over the course of 1 hour. Stirring iscontinued for 2 hours'.

-a.:-l 00 g of the solution'thuspreparedareremoved ,and this sample isintroduced into a flask; 0;85 g of for-- mic acid is added with stirringand the whole is left to stand for 4, hoursv in a chamber kept at 25 6.-

b. The same procedure as in (a) is followed, usi'g ism'eas'ured in thesam way. The following results, ex-

pressed in poisesj'are o' btainedf' i' I The procedure,- indicated inExample 1 is followed, but replacingthe ortho-cresol.bytechnical cresoland using 9.1 g .of the acids instead. of 0.85. g as in Example 1 Thefollowingmesults, in ,poises, .are obtained.

After I l v ,7 Viscosity A 5 lnitial. I day; 4 days Reference solution'17 6 -20) A K 200 i w Composition with., i

formic acid 27 II I I7 Composition with acetic acid r 55 56 EXAMPLES.The procedure indicated in Example 2 is followed, using a batch ofpolytrimellitimide amide containing 7.5% by weight of NMP and 1.6% byweight of water, and having a reduced viscosity (measured as before) of48 cm /g. Different amounts of formic acid are added and the viscosityat. 25 C-of the compositions thus obtained is measured, the measurementsbeingmade on an EPRECHT Rheomat l5 viscometer equipped with a cell C anda moving component C.

The following results, expressed in poises, are obtained.

l: by weight of formic acid relal 2 tive to the solution Eprechtviscosity as l ss 70 4| -20 v 10.2 7.9

, EXAMPLE 4 I -The procedure indicatedin 'Example3 is followed, usingvarious'acids in an amount of 9.1% by weight relative to the solution. I

The following results, expressed in poises, are obtained: 1

reference: 135

,formicacid: 20

acetic acid: 44

propionic acid :'-43,

acrylic acid: 47

EXAMPLE p The procedure indicated in Example l is followed,

but with a batch of polytrimellitimide-amide containing 6.6% by weightof NMP and.2.9% of water and having a reducedviscosity of 38 cm /g. Thepolymer is dissolved in ortho-cresol at C; and then formic acid (0.86%by weight relative to the solution) is added to .a part of thissolution. The viscosity of the reference solution and of the compositioncontaining formic acid, is then measured, firstly immediately after thesolutions have been prepared and then after 2 and 3 days. The viscosityis measured on a Brookfield viscometer at 20 revolutions/minute; theresults obtained are expressed in, poises:

After After Viscosity Initial Z'days 3 days REference 810 1,000 1,186With 0.86% i of formic acid 226 260 270 EXAMPLE 6 16.5 g of the samepolytrimellitimide-amide as that of Example 5 are placed in 200 cmflasks. 83.5 g of ortho-cresol and a varying amount of formic acid areadded. They are placed on rollers and-are left to rotate overnight at50C.

The viscosity is measured on a Brookfield apparatus at 25C at 20revolutions/minute, firstly immediately after the preparation iscomplete and then after being stored for 6 weeks at 25 C.

The following results, in poises, are obtained.

% of formic acid rel- 0 ative to the solution Initial viscosityViscosityafter 6 weeks a. The composition containing 2.23% of formicacid is applied to an annealed copper wire of diameter 0.8 mm, at therate of 10 m/minute, by means of a vertical SICME machine equipped withan oven 6 m long. The oven is divided into 4 zones, the temperatures ofwhich are respectively 170, 230, 290 and 360. A film of thickness 0.03mm is deposited in 6 applications.

b. The procedure is carried out with the same composition', but withoutformic acid. In order to to achieve the same thickness, eightconsecutive applications must .be carried out.

At the outlet from the oven, the quality of the lacquer is checkedcontinuously on a Spark Tester apparatus such as that described in thesecond conference of Electrical Insulation Conference, Boston, September3 With the first composition, the number. of defects per meters is lessthan 20, whilst with the composition without formic acid, the number ofdefects per 100 meters is greater than 50.

The addition of formic acid makes it possible to improve the appearanceof the lacquer and to remove the bubbles to a large extent. Moreover,the flexibility is improved.

EXAMPLE 7 A composition containing 30 g of the samepolytrimellitimide-amide as that of Example 1, 70 g of ortho-cresol and10 g of formic acid is prepared.

A solution with a viscosity of 126 poises is thus obtained and is caston a glass plate in order to form a film of thickness 0.2 mm.

The film and support are then placed in a ventilated oven for 30 minutesat 120 C and then for 30 minutes at l50 C. The film is then detachedfrom the glass plate and is stretched between 4 clips, and the drying iscompleted in an oven at 300 C for minutes. A red-brown film, ofthickness approximately 0.06 mm, with a pleasing appearance, is thusobtained.

We claim:

l. A low-viscosity composition which comprises an 30% by weight based onthe weight of polymer and solvent.

3. A composition according to claim 1 in which the carboxylic acid isformic acid.

4. A composition according to claim 1 which the polymer is apolytrimellitimide-amide.

5. A composition according to claim 1 in which the phenol is a cresol.

6. Process for lowering the viscosity of a solution of an imide-amidepolymer in a phenolic solvent which comprises at least one phenol whichhas a melting point below 50C., which process comprises adding asaturated or ethylenically unsaturated carboxylic acid with up to 6carbon atoms selected from formic acid, acetic acid, propionic acid,butyric acid, acrylic acid, crotonic acid and methacrylic acid to thesolution in an amount from 0.1 to 50% by weight based on the solutionthe viscosity of which is to be lowered.

7. A method of coating a substrate which comprises applying thereto acomposition as defined in claim 1 and evaporating the solvent.

8. A method according to claim 7 in which the substrate is a metal wire.

9. A metal wire coated with a composition as defined in claim 1.

1. A LOW-VISCOSITY COMPOSITION WHICH COMPRISES AN IMIDEAMIDE POLYMERDISSOLVED IN A PHENOLIC SOLVENT WHICH COMPRISES AT LEAST ONE PHENOLHAVNG A MELTING POINT BELOW 50*C., AND A STAURATED OF ETHLENICALLYUNSATURATED CARBOXYLIC ACID WITH UP TO 6 CARBON ATOMS SELECTED FROMFORMIC ACID, ACETIC ACID, PROPIONIC ACID, BUTYRIC ACID, ARYLIC ACID,CROTONIC ACID AND METHACRYLIC ACID IN AN AMOUNT FROM 0.1 TO 50% BYWEIGHT BASED ON THE WEIGHT OF POLYMER AND SOLVENT.
 2. A compositionaccording to claim 1 in which the carboxylic acid is present in anamount from 0.1 to 30% by weight based on the weight of polymer andsolvent.
 3. A composition according to claim 1 in which the carboxylicacid is formic acid.
 4. A composition according to claim 1 which thepolymer is a polytrimellitimide-amide.
 5. A composition according toclaim 1 in which the phenol is a cresol.
 6. Process for lowering theviscosity of a solution of an imide-amide polymer in a phenolic solventwhich comprises at least one phenol which has a melting point below50*C., which process comprises adding a saturated or ethylenicallyunsaturated carboxylic acid with up to 6 carbon atoms selected fromformic acid, acetic acid, propionic acid, butyric acid, acrylic acid,crotonic acid and methacrylic acid to the solution in an amount from 0.1to 50% by weight based on the solution the viscosity of which is to belowered.
 7. A method of coating a substrate which comprises applyingthereto a composition as defined in claim 1 and evaporating the solvent.8. A method according to claim 7 in which the substrate is a metal wire.9. A METAL WIRE COATED WITH A COMPOSITION AS DEFINED IN CLAIM 1.